﻿using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;

using EVEMon.Common;

namespace EVEMon.Common.IgbService
{
    /// <summary>
    /// Listens for IGB client connections
    /// </summary>
    public class IgbTcpListener
    {
        private readonly Object m_syncLock = new Object();

        private bool m_running;
        private IPEndPoint m_listenEndpoint;
        private TcpListener m_listener;

        #region Constructor, Start and Stop
        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="ep"></param>
        public IgbTcpListener(IPEndPoint ep)
        {
            m_listenEndpoint = ep;
        }

        /// <summary>
        /// Start listening
        /// </summary>
        public void Start()
        {
            lock (m_syncLock)
            {
                if (!m_running)
                {
                    m_running = true;
                    m_listener = new TcpListener(m_listenEndpoint);
                    try
                    {
                        m_listener.Start();
                        BeginAcceptTcpClient(false);
                    }
                    catch (SocketException)
                    {
                        // null out the listener then notify the user
                        m_listener = null;
                        EveClient.Notifications.NotifyIgbServiceException(m_listenEndpoint.Port);
                    }
                }
            }
        }

        /// <summary>
        /// Stop listening
        /// </summary>
        /// <remarks>
        /// My wife thinks I use this function too often
        /// </remarks>
        public void Stop()
        {
            lock (m_syncLock)
            {
                if (m_running)
                {
                    m_running = false;
                    if (m_listener != null)
                    {
                        m_listener.Stop();
                        m_listener = null;
                    }
                }
            }
        }
        #endregion

        #region Client Connected
        /// <summary>
        /// Begin accepting a client connection
        /// </summary>
        /// <param name="acquireLock">require lock on object</param>
        private void BeginAcceptTcpClient(bool acquireLock)
        {
            if (acquireLock)
            {
                Monitor.Enter(m_syncLock);
            }
            try
            {
                IAsyncResult ar;
                do
                {
                    ar = null;
                    if (m_running)
                    {
                        ar = m_listener.BeginAcceptTcpClient(new AsyncCallback(EndAcceptTcpClient), null);
                    }
                } while (ar != null && ar.CompletedSynchronously);
            }
            finally
            {
                if (acquireLock)
                {
                    Monitor.Exit(m_syncLock);
                }
            }
        }

        /// <summary>
        /// TCP client connection acceptance has completed
        /// </summary>
        /// <param name="ar">results</param>
        private void EndAcceptTcpClient(IAsyncResult ar)
        {
            lock (m_syncLock)
            {
                // Has the client been stopped ?
                if (m_listener == null) return;

                try
                {
                    bool inLock = ar.CompletedSynchronously;

                    TcpClient newClient = m_listener.EndAcceptTcpClient(ar);
                    OnClientConnected(newClient, !inLock);
                    if (!ar.CompletedSynchronously)
                    {
                        BeginAcceptTcpClient(true);
                    }
                }
                catch (Exception e)
                {
                    ExceptionHandler.LogException(e, false);
                }
            }
        }

        /// <summary>
        /// Triggered on client connection
        /// </summary>
        /// <param name="newClient">the client</param>
        /// <param name="acquireLock">require lock on object</param>
        private void OnClientConnected(TcpClient client, bool acquireLock)
        {
            if (acquireLock)
            {
                Monitor.Enter(m_syncLock);
            }

            try
            {
                if (m_running && ClientConnected != null)
                {
                    ClientConnected(this, new ClientConnectedEventArgs(client));
                }
                else
                {
                    try
                    {
                        client.Close();
                    }
                    catch (SocketException e)
                    {
                        ExceptionHandler.LogException(e, false);
                    }
                }
            }
            finally
            {
                if (acquireLock)
                {
                    Monitor.Exit(m_syncLock);
                }
            }
        }

        public event EventHandler<ClientConnectedEventArgs> ClientConnected;
        #endregion
    }
}
